LAUSR

INTRODUCTION The course of consecutive COVID-19 waves was influenced by medical and organizational factors. OBJECTIVES to assess the outcomes of in-hospital COVID-19 cases within the first three waves of the pandemic. PATIENTS AND METHODS A retrospective medical record analysis of all COVID-19 patients admitted to the University Hospital (UH) in Krakow, the reference COVID-19 hospital in Lesser Poland, between March 1' 2020 - May 31' 2021 was performed. The waves were defined as 1 - 3, respectively: March-July 2020, August 2020 - January 2021, February 2021 - May 2021. Patient's characteristics and outcomes of waves 1-3 were compared. RESULTS Data analyses included 5191 COVID-19 patients. We defined differences in age (mean [SD] were 60.2 [17.3] years. Vs. 62.4 [16.8] years vs. 61.9 [16.1] years respectively for wave 1 vs 2 vs 3, P = 0.003); gender distribution (proportion of women: 51.4% vs. 44.2% vs. 43.6%, P = 0.003); inflammatory markers and oxygen saturation (the lowest and the highest for wave 1, respectively, P <0.001). The hospital death rate in subsequent waves was: 10.4%, 19.8%, 20.3%; P <0.001. Despite similar patients' characteristics, the length of the hospital and Intensive Care Unit stay was shorter for wave 3 compared to wave 2. The risk factors for in-hospital death were: advanced age, male sex, cardiovascular or chronic kidney disease, higher C-reactive protein level and hospitalization during the 2nd or 3rd waive. CONCLUSIONS We identified differences in patient's clinical characteristics and outcomes between consecutive waves, which probably reflect changes in terms of COVID-19 isolation policy, hospitalization indications and treatment strategies.